Apparatus for liquefaction of gases.



G. A. BGBRICK.

APPARATUS POR LIQUEFAGTION OF GASES.

APPLIOATION FILED DBO.13. 1904.

Patented June 8, 1909.

5 SHEETS-SHEET l.

G. A. "3-013310K. APPARATUS FOR LIQUEFAGTION 0I' GASES. APPLICATION FILED DEO. 13. 1904.

Patented June 8, 1909.

5 SHEETS-SHEET 2.

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G. A. BOBRIGK. APPARATUS FOR LIQUBFAGTIGN 0F GASES.

APPLICATION FILED DEO.13. 1804.

924, 1 37. Patented .me 8, 1909.

5 SHEETS-SHEET 3.

Patented June 8, 1909.

5 SHEETS-SHEET 4.

fave/2%@ y G. A. l130131110X. APPARATUS POR LIQUEFAUTION 0F GASES. l PPLIQATION FILED DEG. 13, 1904. 924,137,

Q9" 'jai G. A. BOBRIGK.

APPARATUS FOR. LIQUEFACTION 0F GASES.

' APPLICATION FILED DEO. 13. 1904.. f 924, 1 37. Patented June 8, 1909.

5 SHEETS-SHEET 5.

UNTTED ,g sTATEs PATENT crimen.

GABRIEL A. BOBRICK, OF-LOS ANGELES, CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO UNITED STATES LIQUID AIR dz OXYGEN COMPANY, O`l LOS ANGELES, CALIFORNIA,

A CORPORATION OF CALIFORNIA.

APPARATUS FOR LIQUEFACTION OF GASES.

Specification of Letters Patent.

Patented June 8, 1909.

Application filed December 13, 1904. Serial No. 236,741.

To all whom it 'may concern:

Be it known that I, GABRIEL A. Bosnien, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have invented new and useful Improvements in yA paratus for the Liquefaction of Gases, of w nch the following is a specification.

The primary object of my invention is to provide a system and apparatus by which gases and mixtures of gases having a low critical temperature below zero F., ora high critical pressure, above 150 pounds to the square inch, or both, such as oxygen, nitrogen, air, etc., can be liqueiied in large quantities at .a reasonable cost; and by which system the present great cost of installing machinery and apparatus suitable for oompressing gases to exceedingly .high pressure can be reduced to a minimum; also the necessity of providing exceedingly strong. ap-

paratus and heavy or thick-walled temperaturey interchanging coils which are not only' costly but ,detrimental to the proper interchangeI of temperature, can be obviated.'I

Anotherobject of my invention is to effect the necessary lowering in temperature by adiabatic expansion means which have a much greater thermal efficiency than the free expansion means now generally employed in the manufacture of liquid air, etc.

Another object of my invention is to provide means by which that portion of the gases which assumes the liquid state and such admixtures as carbon dioxid, for instance,

which assumes the solid state in the pipes,

channels or chambers above the expansion devices, can tbe separated and automatically removed from the unliquefied gases and therey by prevented from passing into or through the expansion devices.

Another object of my invention is to provide means by which the' )recess of manufacturing liquefied Gases, and particularly liquid air, can be mad-e continuous, obviating the necessity of stopping at intervals for the sole purpose of thawing out and .removing from the pipes of the liq uefi-er the frozen particles of moisture and lubricating oil carriedthereinto by the compressed air, or oil alone in the case of compressed gases free from moisture,

etc.

A further object of my invention is yto provide means by which a part of the air or gas can be used more than once in regenerative cooling, by a succession ol' expansion and temperature-interchanging devices, thereby increasing the capacity and elliciency of the system. y

A further object of my invention is to provide means by which all or part of the heat generated in the process of compressing the air or gas caribe utilized for increasing the efficiency of the power cylinder of the internal combustion engine.

To sim )lify the specification l will describea plant for the manufacture of liquid air, but it is to be understood that the apparatus used for liquefying air o'r any gas within the range of its capabilities, and that the use inthis specification of the terms air and"gas is not intended as any limitation of the invention.

Certain mechanical expressions of the inventive idea involved are shown in the accompanying drawings, which are designed merely as illustrations to assist in the description of the invention, and not as defining the limits thereof.-

The accompanying drawings illustrate the invention, and referring to the. same:-Fig ure 1 is an elevation somewhat diagrammatic of the complete s stem of apparatus, some ol' the parts being s iown in section. Fig. 2 is a vertical section of the liquefier proper. Figs. 3 and 4 are detail sections of a modified form of separator. Fig. 5 is a View similar to Fig. 1 showing a different embodiment of the invention. Fig. 6 is a verticaly section of the liquefier shown in Fig. 5. Fig. 7 is a diagrammatic representation of a system adapted for large plants.

Referring to Fig. 1, an air compressor is designated in a general way at 1 comprising power-cylinder 2, preferably an internal combnstion engine, and compression cylinders 3 and 4,with intercooler 7, all arranged in the usual manner. The cylinders are 'waterjacketed and water sup ly is circulated throughv such jackets and t rough the intercooler, and discharged by pipe connections 8. It will be .understood that the number ol' stages in the compressor will depend on the pressure used. From the cylinder 4 the compressed air is led by a pipe 9 to an oil and moisture separator 10, whence it passes by a pipe 11 to a cooler or temperature-interchanger 12 for absorbing the heat remaining from 'final compression. Said cooler is referably so constructed as to abstract this ieat without recourse to cooling w ater or any cooling or heat-abstracting agent or medium other than air. lt will be understood that for this purpose a more extended surface will be necessary than is required with a cooler using water as a heat-absorbing medium, and since every internal-combustion engine requires air for producing the explosive mixture, and since the higher' the temperature of the air within certain practical limits the greater is the efficiency of said engine, l prefer to connect the temperature-interehanger l2 to the intake-pipe i3 of the cylinder' 2, said temperature-interchanger l2 being of any suitable pattern, made in a cylindrical or any other form. rl`he pipe l5 carrying the compressed air to be cooled, may he made in the `forni of a coil and located within a casing la. The air for the internal-combustion cylinder is taken from a suitable place through pipe i6. it may be pbserved that the compressed air to be cooled ilows in direction opposite to that of the air to be warmed for the internal-combustion cylinder. An interchange ol temperature takes place, and the compressed air upon leaving the temperatureinterchanger is of about the same temperature as the atmosphere. This temperatureinterchanger la thus serves a double purpose, the heat of compression being bstractcd from the compressed air at the -e time that the air for the j@ er-cylinder 2 is being warmed. 'eoling water is saved,

rl`l1e cost oi and the efficiency of the internal-combustion engine is increased. t is to be understood that if the power necessary l'or driving the compressor is derived from any other source than that of an internal-combustion engine directly connected to said compressor then said temperature-interchanger may be connected to the intake-air-pipe of any internalcombustion engine located on the premises or outside within a reasonable distance from the compressor or instead of the temperature-interchangershown, any other cooler, such as an ordinary water-cooler, may be used. Part of the moisture and oil contained inthe com ressed air will condense in the coil l5, and will flow by gravity hack into Separator or trap 10 from which it may be removed from time to time through valve or cock 33. From the temperature-interchanger 12 the air passes by the pipe 17 into trap 24, thence into the counter-current ap aratus called the forecoolers associated with the li uefier proper.v

n order to perform the cooling action in this apparatus in the most efficient and convenient mannerl find it desirable to divide such apparatus into a plurality of sections which will successively reduce the temperature of the air in the following manner The lirst section indicated at i8 serves to re- ,vapors contained therein.

' vided for these multiple pipes 22.

duce gradually the temperature of the compressed air to a stage approaching the freezing or solidifying point of water or aqueous The second seetion indicated at 19 serves to further reduce the temperature of such compressed air to a point below the freezing or solidifying pointal'oresaid; while the third section, indicated at 20, serves to still further reduce the temperature of the com ressed air to a weint at which it is tdapte to.enter the liquelier proper, practically free from moisture and vaporized oil. The lirst section 1S is desirably constructed with multiple tubes or conduits 22 each of comparatively small diameter, thereby providing a maximum heattransferring effect between. the gas flowing in these conduits and the surrounding medium. rlhe outer envelo or conduit 2l surrounds these multiple tu .ies 22 andserves for the passage of a return current of cool air, as hereinafter described. Headers 23A are proinasmuch as the compressed airis cooled in this section i8 to approximately the freezing point of water, it follows that there is no possibility of deposition 'of ice or snow in the pipes thereof, and therefore the latter may be made of comparatively small diameter without interfering with their regular and continuous operation. The greater partof the volatilized oil is removed from the air in this section and collected in traps 2l which are placed at the lowermost points thereof to enable the oil and water to collect and be drawn oil from time to time through valves er cocks S3. Thenext section 1Q carries the refrigeration beyond the freezing point of water, and it is, therefore, not desirable to provide such section with small pipes similar to those of section 1S as the deposition of ice and snow therein would soon clog the pipes and interfere with the continuous operation, although in,J large plants comparatively large pipes arranged in multiples may be used. rlhe internal pipe 2G of section 19 is, therefore, preferably a single conduit of relatively large diameter so as to allow deposition of ice and 'snow on its inner walls without interfering with the free passage of compressed air therethrough. lt will be understood that in the regular operation of the apparatus a considerably reduced amount of the aqueous vapor and oil will be contained in the compressed air when it reaches this section, so that only a comparatively very thin coating of ice and snow will form on the inside walls of pipes 2G, and part of this may be clown out from time to time during the operation of the plant by opening;r the valves 33 ofthe traps 28 which are located at the lowermost points of this section.

27 designates the outer pipe or return ourrent conduit of section 1Q.

SectionQO is shown as similar in construclll) Ilm

lllfi llll near 'as it possibly cank be done in practice,

il U

Jfree from aqueous vapor and oil, and has also been relieved of part vof its carbon-dioxid. 1t is, therefore, practicable 'to construct the internal conduit of the liquefier with multiple pipes or conduits 37 of relatively small diameter 'for the passage of the compressed.

air, thereby obtaining the result above set forth of increased heat-transmitting power. At the lower end the pipes or conduit 37 lterminate in a header 38 which is connected direetly'or by pipe 39 to a separator 10 from which connection 41 leads to a trap 12, and connection 51 to an expansion device preferably a thermo-dynamic engine 53 in which the compressed air is made to expand adiabaticallyor nearly so. `My reasons for employing an adiabatic expansion device for the free expansion means, now in general use, in the manufacture of liquid air and other liqueiied gases having ,low critical tempera-- tures, are these 1t is known that air upon lree expansion from a space maintained at a higher'pressure into a space maintained at a lower pressure,l drops in temperature, and

that the drop in temperature due to internal work performed by such expansion, is expressed 1n the formula fall in temperature; 'and theoretically, ii'l p, p one atmosphere, then (the critical temperature of air).

On the other hand, if the air is expandedr grdiabatically in a thermo-dynamic engine, doing external work., and no heat is transferred from or into the air during the opera.- tion, then according to the formula of relations betweenpressures and temperatures.

sion

the final temperature of the air after expanin which t, and p, are the absolute temperature' and pressure of the air before expansion, and t andp the absolute temperature and vpressure of the air aft-fer expansion, the exponent I 0.291 of which (the ratio of the s eciiic heat of air at constant pressure to t at at constant volume).

d= 9.3 deg. F. for a ratio of 2, d =195 deg. F.1`or a ratio of 5, 255 deg. F. for a ratio of 10, 285 deg. F. for a ratio of 15.

1n practice the drop in temperature will be 4very much less. A loss of from 15% to 50%, due to transmission of heat, inefficiency ol' motor, imperfect insulation, etc., maybe expected.

1n my systemV I prefer to operate the thermodynamic engine with ratios of from to 15, although higher or lower ratios may be employed, but assuming that 1 operate the engine with a ratio of expansion of 10, and assuming also that the temperature of the air before expansion is 62 F., and the thermal losses then the drop in temperature will equal about 127o F., as against a drop in temperature ol about 4.5o F. due to l'ree expansion under the same conditions. Besides the great gain in thermal advantages, about 50% of the work done in compressing the airmay be recovered. The above calculations are only approximately correct. in my present invention I make use ol' the counter-current, self-intensive principle, emloying, however, las above stated, an adi-abatic expansion device for the free expansion means, and my reasons for interposing a trap and separator between the coil, pipe or chamber carrying the compressed 'airand the thermodynamic englne, are these :-1n counter-current, sell-intensive apparatus operated by free expansion means, the small quantity ol' liquid air, if any, which may accumulate above the expansion valve, if free from frozen carbon dioxid, would not seriously interfere with the proper operation of suoli means, but since the thermal etliciency of an adiabatic expansion device is so much greater than that ol' free expansion means, a considerable quantity ol air will assume the liquid state in the pipe or coil above the adiabatic expansion device, and this liquid, if not removed, would seriously interfere with the proper operation ot' the adiabatic expansion device, if it did not practically make it inoperative. It must be understood, however, that only part of the compressed air can assume and remain in the liquid state above the throttle valve oi' the expansion device for the reason that a considerable quantity of heat equal to the latent heat of evaporization ol' liquid air will be liberated the moment the change from the gaseous to the liquid state takes place.

To make the apparatus commercially operative the liquid air and frozen carbon dioXid must be separated and removed from the coil so as to operate the adiabatic expansion device by compressed gaseous air only. For this purpose I employ a. separator and trap, singly or in multiple.

I do not .limit my invention to any special or particular construction ol' thermodynamic expansion device, separator or trap. Any suitable device or devices which will answer the purpose for which they are intended, may be employed; nor do I limit my invention to any Inode of installation. The adiabatic expansion device, separator or trap, or either ol' them, may be placed within the li ueiier pro 3er, or they may be placed outside of the liquelier proper, properly insulated and connected to the counter-current coil or coils oll the so-called liqueiier.

Separator 4() consists of a vessel having the inlet connection 39 and the outlet connection for the gas 51 above the liquid outlet connection 41. In this separator 40 the liquid separates from the gaseous air by gravity. The li uid iiows through pipe 4l into trap 42 Whic i consists of an outer closed vessel 43 and an inner vessel or iloat 44 open at the top and movable vertically in the outer vessel, being guided therein by guide means 45 at the side, 'and a guide pin 45n at the bottom working in a socket 45".

46 is a conical projection or valve plug on the bottom of vessel 44 which cooperates with a conical seat at the lower end of pipe 47 to form a valve 48 for controlling communication to said pipe.

The liquid air upon entering vessel 43 raises the inner vessel 44 and thereby closes the valve 48. When the level of the liquid reaches the top of vessel 44 it overflows into it, and upon reaching a certain level the vessel 44 sinks and thereby opens valve 48.

y The pressure maintained in the trap 42 is the same as that of the compressed air, and

owing to this pressure the liquid is forced out through pipes 47 and 4Q into separator 50 in which a lower pressure is maintained.

49a is a valve in pipe 49 controlling` communication between trap 42 and separator 50 and 42 is a connection and valve leading from trap 42.

The compressed air iiows through pipe 51 to the adiabatic expansion device 53 which may consist oi' any suit-able thermo-dynamic engine, expansion engine, motor or turbine. The throttle valve is shown at 52, and the stem 54 oll this valve projects outside of the casing or the inelosure 55. In the adiabatic expansion device the compressed air may be allowed to expand from about 30() pounds to the square inch to a gage pressure ol about pounds to the square inch, and by doing so it performs external work and drops in temperature. The exhaust l'rom the adiabatic expansion device, both liquid and gaseous air, flows through pipe 56 into separator 5() where they meet the liquid and gaseous air coming from trap 42 through pipe 4l). It is understood that although liquid air alone can be discharged through the valve 4S oll the trap 42, owing to the di llerence in pressures maintained in trap 42 and separator 50, so much ol' the liquid will evaporate upon passingl valve 4S as is necessary to reduce its temperature to that ol liquid air maintained under a pressure ol' 6() pounds to the square inch. The liquid air from separator 50 i lows through pipe 57 into. trap 5S, similar in construction to trap 42.

57a is a valve in pipe 57 controlling communication between the separator 50 and trap 58, and 50 is a connection and valve leading from separator 50.

Part oi` the cold, unliqueiled air passes from separator 50 through valve 5S) and connection GS) into conduit GO which incloses conduit 37, as will hereafter be described, and part oi' it is allowed to expand through valve 6l into receiver 63 Vl'rom a pressure ol' about 60 pounds to the square inch to about atmospheric pressure. rater 50, upon expansion through throttlevalve. 6l drops in temperature. Part oi it liqueiies, and together with the unliqueiied air' itows through connection (i2 into receiver 63. charged through connection 64 into receiver 63 in the manner heretofore described l'or trap 42. Owing to the dii'l'erenee in pressures maintained in tra i 5S and receiver G3 so much of the liquid relleased l'rom pressure ol` about 60 oundsto the square inch to about atmosp ieric pressure will evaporate as is necessary to reduce its temperature to that of the temperature of liquid air at atmospheric pressure; viz., about 312.()l deg. below zero F. rI`he liquid air may be withdrawn from receiver 63 through valve 65u and connection 65. The unliqueiied cold air The air l'rom sepa- The liquid air from trap 5S is disfrom receiver 63 flows through connection 66 into conduit 67 which envelops or surrounds conduit 60. The cold air oi' the .pressure of about 60 pounds to the square inch flows through conduit or channel 60 in a direction opposite to that of the incoming compressed air, which is of a higher temperature and which flows through conduit or pipes 37, and in doing so it absorbs heat from it and gradually reduces 'its temperature. The cold air in conduit 67 iiows in the same direction as that in conduit 60 and serves as an insulator for the air within thev inner channels or conduits 60 and 37 as well as a heat-abstracting medium.- Pipe connections or passages 68 lead from the respective high pressure, intermediate pressure and low pressure chambers and channels 51, 50 and 63, and are connected to suitable pressure ages to enable the attendant to ascertain t e pressures in the respective chambers. The entire system of piping of the li ueiier is inclosed or embedded in suitable eat-insulating material,

.. indicated at A, which in turn is inclosed in casing '72.

cools section 19.

From the return conduits 60 and 67 of the liqueiier the ex anded air is led by pipes -70 and 71 throug the external conduits of the counter-current apparatus above referred to. The pi )e 7'1 from the low-pressure conduit 67 oi' tlie liqueier leads to one end of the external conduit 21 of section 18 of the counter-current apparatus, connection being made from the ot er end bf such conduit 21, through the pipe 73 and valve- 74, to the intake-p' e 75 of the" compressor. The pipe 70 leads from the intermediatepressure conduit 60 of the liqueiier to Aone end ol the external-pressure conduit 27 of section 19 'of the counter-current apparatus.

The thirdk section 20 of the counter-current apparatus is desirably -cooled by the utilization of the same current of air that This air at the intermediate pressure, in passing through section 19, has absorbed so much heat that t enable it to be used in furtherlcooling-i it is necessary to reduce its temperature by allowing it to expand. Such expansion may be performed in any suitable apparatus, but I preferto provide for this purpose a thermo-dynamic engine or expansion device 80 wherein the air is caused to perform external work inthe act of expansion. The outer casing 27 of section 19 is connected to the thermodynamic engine by pipe 76, valve 105, heater l1 00, pipeI 79, valve 106 and pipe 81. Assuming that the return current of air of the intermediate pressure in Yflowing through the return conduit 6() of the liqueiier and return conduit 27 of section 19 and all connections to thel thermodynamic engine 80, absorbed enough heat to reach a temperature of about 62 F., then according to the formula of relations between pressures and temperatures due to adiabatic expansion, as heretofore cited, the drop` in temperature for a ratio of expansion of 5 will equal about 195 degrees F., (in practice about 15% less), givin a i'inal temperature of about 1,04 degrees be ow zero F. Besides this great drop in temperature, the eiiect of which will be utilized for cooling section 20, about of the work done in the compressor while compressing this amount ofA air to a gage pressure of pounds to the squareinch, may be recovered'.

`The exhaust side-of, the thermodynamic` engine 80 is connected by pipe 82 to a trap 83 provided'with a draw-ofi cock 84 which in turn is connected by pipe 85 to one end of the external conduit 31 of sectionv 20, the other end of said: external conduit31 being connected through pipe 92 and valve 93 to the pipe 71 leading to the outer conduit of section 18, from which connection is made as above described to the low-pressure compressor cylinder. Valves 94, 95, are provided in pipe 71, one on each side of the junction with pipe 92. The air that passes from the expansion engine to the final section 20 'of the counter-current apparatus may be assumed to have a temperature of about 104 degrees F., and the compressed air that passes from section 20 will, therefore, enter ture, say from 50 degrees F., to 75 degrecs F., so that it will not be possible for it to contain aqueous vapor or oil to an extent sufficient to interfere with the operation, it

the liquefier at a somewhat higher temperabeing understood that the temperature of theV outgoing compressed air from section 2() will vary with the temperature of the incoming air and the roportion of the air in the outer conduit to t at in the inner one. From twotliirds to four-fifths ofthe total amount of air expanded in motor 53 passes thus through the return conduit 31 of section 20 and leaves the same at from 0 degrees F. to 20 degrees F., and it is then led through pipe 92 and valve 93 so as to join the balance of the air passing through pipe 71 which may be assumed to have a temperature of about 80 degrees F. The combined quantit of air will then pass to section 18 so that al the air delivered by the compressor, except that which has been liquefied, or in any other Way wasted by blowing out, etc., is utilized in cooling this i section. The temperatures above given are only approximate.

N77 indicates a val/ve controlling a direct connection from pipe 76 to the high pressure compressor cylinder 4.

88 indicates a valve whichV controls communication from the .intake pipe 75 to the outer air; this valve is a self-regulating check valve set to a certain pressure so as to admit only the required amount of atmos heric air.

97, 98 and 99 designate draw-ofi valves or cocks communicating with pipes or conduits 86, 76 and 73, to enable the gaseous contents thereof to be withdrawn when desired.

Taps or cocks 104 are provided at the lowest points of the return conduits 21, 27 and 31 to draw off condensed substances which may accumulate. It will be understood that foreign substances will not deposit in these pipes except under unusual conditions.

In practice, if operating with atmospheric air, a gas rich in nitrogen may be drawn y from cocks or valves 97 or 98, or a gas rich in oxygen may be drawn from cock 99 as hereinafter explained. Connections may be made with gasomet'ers or other means for storing the gases for future use.

100 designates a heater or warmer that may be interposed in the connection 79 from pipe 76 to pipe 81 whereby the air that is delivered at intermediate pressure to the motor or expansion engine 80 may be warmed before expansion so as to increase the efficiency of the engine, or not to permit too low a temperature therein. I prefer to keep the air entering the engine 80 at a tem perature of about 60 degrees F. although a lower or higher temperature may be main,- tained. This warmer or heater may absorb the heat 'from the surrounding atmosphere, or, as shown, may be provided with an external casing 101 through which water or other medium is `circulated by pipe connections 102, and the outlet of said casing may be connected through valve 110 with the water supply pipes 8 of the compressor, so as to utilize the same water for theA compressor. A Water supply pipe 107 and valves 108, 109 are provided for enabling the circulating water to be supplied to the compressor when the device 100 is omitted or not in use.

115 are tubes'inclosing the shaft 116 of the motor 53, so as to prev ent the revolving shaft from coming in contact with the insulation. The bearings 117 of the motor which require oiling are outside of the casing 55.

The mechanical energy developed by themotors or expansion engines 53 and 80 may be utilized in any suitable manner.

It will be understood that the liqueier and the entire regenerative apparatus, including the cooler sections 1S, l19 and 20, and their traps, are properly protected from absorption of heat from the outer air by thorough insulation thereof in well known manner. The expansion engine 80 is also insulated. T0 avoid confusion, the insulating materials a and A are mostly omitted from the views.

To construct and successfully and eco- `nomically operate a plant for the manufacture of liquid air by the adiabatic expansion, accumulative, self-extensive or regenerative process, or for the manufacture of commercial gaseous-oxygen and nitrogen which involve, first, the liquefaction of air and then its separation into commercial oxygen and nitrogenby fractional distillation; and to keep the apparatus in continuous operation,

jit is essential-Firstz-That means should l be provided for the total removal of the heat due to the last compression and before the compressed air enters the liqueiier. Second: That the compressed air before entering the ,liquefier should, as nearly as practicable, be

tained therein and from the oil used in lubricating the cylinders of the compressor. Third: As much as possible of the carbon dioxid, liquid or solid, should be removed from the compressedair before it reaches the liquefier, and practically none should be permitted to enter the adiabatic expansion devices. Fourth: A trap or traps should be located at any point or points in the system Where there is an upward bend of a junction of descending and ascending pipes. Fifth: Means should be provided for the removal of that part of the air Which assumed the liquid state before reaching the expansion device. Sixth: All expansion and counter current means should be thoroughly insulated from the heat of the outer atmosphere, andthe same is true of the pipes and traps carrying air at a temperature below 32 degrees F., except at the outlets.

The operation of the apparatus for the production of liquid air and commercial gaseous oxygen and nitrogen may be described as follows; Valve 88, admitting atmospheric air to the compressor will, in general, be open. In starting, valve 35 leading to the liqueier, will be closed,-valves 91 and 106 admitting com ressed air directly to the motor S0 from the ast cooler section 20, will be opened. Valve 111 may be opened and valves 93, 74, 105 and 77 closed so as to deliver the exhaust from this motor through the external conduit of section 20 directly back to the co1npresser. Under these conditions, only section 20 will be used in cooling. Atmospheric air will be drawn in through valve 88 and will be subject to successive coinpressions in the cylinders 3 and 4 of the. compressor to a pressure of about 300 lbs. to the square inch, the heat due to compression being absorbed by thc water jackets and inter-cooler up to the last stage, from which the compressed air is discharged in heated condition, only so much of the heat of the last com ression having been absorbed as can be ta en up by the water jacket of, and radiated and conducted from the high pressure cylinder. From this cylinder the com* pressed air )asses to the trap 10 where it parts with tie oil carried over in a liquid form, and owing to the relatively lower teinperature of the tra the compressed air also parts with part o its moisture, and then passes through the preliminary cooler 12, wherein it interchanges temperature wil h the. air drawn through pipe. 16 by the cylinder 2 of the internal conllnlstiou engine and is cooled to about the temjwrature of the atfree from the aqueous vapor or moisture conl mosphere. The compressed air` then ows through pipe 17 into trap 24 and through conduit 22 of section 18. The moisture and vaporizing oil which have condensed during the process of cooling in interchanger 12 .Will deposit in traps 10 -and 24, for it is Well known that when air containing aqueous va or is cooled, the temperature of the vapor is owered with the result that its density is increased until the vapor reaches a maximum density for the corresponding temperature. If the temperature is still lowered, part of the vapor wil condense, and if the cooling is gradual and the flow of air is slow and takes place in vertical or inclined pipes provided with traps, the condensed vapor will flow down into the traps from which it may be re'- moved. Frqm conduit 22 the compressed air llows into and through conduit 26 of section 19, then through conduit 30 of section`20 and through connection 90 and valves 91 and 106 to the intake side of the expansion, engine 80. In assing through this engine the air is expan ed adiabatically or `nearly so, and is reduced in pressure and in temperature. The cold, expanded air passes through pipe 82, trap 83, and pipe 85 to the external conduit 31 of cooler section 20, then by pipel S6 and'valve 111 back tothe compressor". 1t will be understood that the compressor Will not, under these conditions, be working to a pressure beyond the capacity of the expan-v sion engine.

The operation described will result in a regenerative or accumulative coolinP of section 20 to a temperature suiiciently `low to deposit tho greater art of the vaporizd oil and aqueous vapor o the com ressed air, so that the compressed air may t en be admitted to the lique'lier without danger of clogging. In

order, however, 'to similarly cool the section 1S in additionto section`20 and thereby l'urther protect the liquefier, the. valves 111, 105, and 77 may be closed, and valves 93, 95 and 74 opened. The cold exhaust lroin the expansion engine 80 will then 'low iirst through conduit 31 of section 20, as above explained, and then through pipes 92, 71 and external conduit 21 -of section 18, and through pipes 73 and 75 to the intake of the low pressure cylinder 3 ot' the compressor. The compressed air having been cooled in c ruiter-current sections lrand 20, as above described, to a suiliciently low temperature, valves 35, 94, 93, 95, 74 and 105 are opened and the valves 91, 1 11 and 77 closed. Valves or cocks 97, 9S and 99 are generally closed. The compressed air now passes through valve 85 into the internal conduit or coil 37 of the liquclier, thence through header 8S and connection 39 into separator 40, and through pipe 51 into motor 53, Where it expands adialmtieally or nearly so, from a Dressureof about 30() lbs. to the's uare inch to a pressure ol' about 60 lbs. to tie square inch. In starting the liquelier, valves 49u and 57a are kept closed until liquid begins to accumulate in separators 40 and 50. The presence of li uid can be detected by o ening valves or coc 's 42a and 50a. Upon t ie appearance of liquid, valves 49a and 57EL are opened so as to establish direct communication between separator 40, trap 42, separator of the ilow of the compressed air within saidv conduit 3.7. An interchange of temperature takes place: the cold air of the intermediate -pressure absorbs heat from the compressed.

air making the cooling e'li'eet of said compressed air accumulative to such a degree that part of it assumes the liquid state in the lower part of conduit 37. The flow of the air from vseparator into conduit 60 is regulated by valve 59. The pressure maintained in conduit 37 is about 300 lbs. to the square inch and that in separator' 50 about 60 lbs. to the s uare inch. Now, since the temperature of iquid air under pressure ot lbs. to the square inch is about 280o below zero F. and since the temperature required tor liquefying air under a pressure of 300 lbs. to the square inch is about 228 below zero F., and as the vapor used for cooling the air in conduit 87 is taken from separator 50, the tem- -erature ofv which vapor is also about 280 low zero F., it follows that the temperature of the cooling medium in conduit 60 is low enough to liquel'y part of the air in the lower part ot' conduit 37. rlhe liquid air from separator 40 ilowstlirough connection 41 into trap 42, and from the latter through connection 49 into separator 50, in the manner heretofore described.

As above stated, from two-thirds lto fouriilths ol the air of the intermediate pressure in separator 50 will be allowed to pass through connection (59 into the intermediate conduit 60; the balance will be allowed to expand freely through valve 61. This air, of a ternpera-ture 4already very low, will upon e'xpansion from a pressure. of 60 pounds to the square inch to about atmospheric pressure, drop in temperature sulleiently to convert part of it into liquid which will, together' with the 'unliquelied air, ilow through counection 62 into receiver 03. 'lhe lliquid air from separator 50 will flow through connection 57, trap 58, and connection 64, also into receiver 63 and may be withdrawn from said receiver through valve (35 and connection G5. The unliquelied air will pass through connection 66 into conduit 67 which surrounds conduit 60. As the air in conduit 67 flows in the same direction as that in conduit 60 it will serve as a'n insulating medium as well as a cooling medium. rlhe attendant guiding himself by the pressure gages, inanipulates valves 52', 61 and 59 so as to maintain the proper relative pressures in the respective conduits, separators, etc. The pressure in pipe 71 leading from the liqueier to valve 94 is' maintained kslightly higher than in pipe 92 leading from cooler 20. From lthe liqueier the air at the intermediate pressure of about 6() pounds to the square inch, passes through pipe to external-conduit 27 of section 19, wherein it absorbs heat from the compressed air, and therefore leaves said section comparatively warm. From conduit 27 the air flows through pipes 76, 79, to the motor or expansion engine 80, where' it is expanded to about atmospheric pressure and considerablyreduced in temperature. The cold exhaust from this engine passes by pipe 85 to cool the section 20,

as above explained. From conduit 31 of section 20 the cold air passes through the pipes 92 and 71 into the outer casing 21 of section 18 and thence through pipes 73 and 75 to the low pressure cylinder 3 of the com presser; or it may be allowed to escape from valve 99. In case all of the air supplied at intermediate pressure is not required for operating the expansion engine 80,' then valve 77 may be opened to cause any desired proportion of such air to pass directly to the intake end of the high-pressure cylinder 4.

The low-pressure cold air from receiver 63 which may comprisefrom one-third to oneifth of the total quantity of air passing into the liquelier, and is of a lower temperature than the air or liquid in separator 50, passes through connection 66 into conduit 67 which surrounds conduit 60, forming a cold envelop for said conduit for its Whole length and (passing out through'pipe 71 and valvev94,

where it mixes with the air coming through pipe 92 from section 20, and, together they pass through valve 95 to the outer casing 21 of the first section 18 of the countercurrent apparatus. Upon leaving this section it passes by pipe 73 and valve 74 to the intake of the low-pressure cylinder 3.

In utilizing this system and apparatus for the separation of atmospheric air into commercial oxygen and nitrogen, the condensed product is allowed to accumulate in receivers 50 and 63. The product of evaporation from receiver 50 will be a gas rich in nitrogen the remaining liquid will be rich in oxygen'. This liquid rich in oxygen will iow, as before described, through trap 58 into receiver 63 in which it will be allowed to evaporate. The

evaporated gases from receivers 50 and 63 will flow through connections and conduits already described and may be withdrawn through valves or cocks 97 and 99. It may be observed that in` this instance trap 58 will prevent the passage of gas, rich in nitrogen, Jfrom receiver 5() into receiver 63; valve G1 may be closed. Vhen making commercial oxygen and nitrogen in this manner, valves 111 and 93 are closed so as to direct the nitrogen from conduit 31 ol` section 20 to valve 97, and prevent it from mixing with the oxygen flowing through pipe 71, while valve 74 .be filled with glass beads or glass wool or any other suitable material, shown at 179 in Fig. 3, so as to enlarge the surface ol contact, or a coil 180, as shown in Fig. 4, may be introduced in said separator communicating with connection 51 so as to permit part of the compressed air flowing through pipe or connection 51 to pass through said coil to impart heat to the `liquid air within receiver 50. 181 is a valve to regulate the amount ol' air to be passedthrough coil 180. rlhc contents from said coil 180 may discharge directly into receiver 50.

It will be noted that there is a connection around the thermodynamic engine that is to say, between the high and low pressure sides of said engine, said connection leading through pipe 41, trap device 42 and its valve 48, and pipe 49 to the separator 50, on the low- )ressure side of the engine, this connection eing closed by valve 49 a until liquid begins to accumulate .in tra i 42. Then enough liquid has accumulated in trap 42 to raise the inner vessel 44 sufliciently to close valve-48, then valve 49CL is opened and the trap begins to automatically discharge the liquid from separator 4() into separator 50. This is an important feature, as it prevents the passage of liquid through the engine. The main difficulty in the use ol' a thermodynamic engine in this connection was the interference with its operation due to presence of liquefied product therein, and the above describe'd automatically opening valve enabled me to overcome this di'hculty.

The above-described system and apparatus for the liquefaction of air or other gases is best adapted for moderate size plants where efficiency is a primary factor and cost ol' installation a secondary but for small plants, or where it is desirable or convenient to operate the plant with comparatively low pressures from 100 to 250 lbs. to the square meh,

the modified system and apparatus illus-I coeler, and 204 and 205 represent the connections for the circulating Water or other heat-absorbing medium. Air is admitted to the compressor through self-regulating valve 188 and connection 175, and is compressed successively in cylinders 201 and 202 to about 150 lbs. to the square inch.. The compressed air from4 cylinder 202 flows through connection 206 and tra 207 into a modified form of `heat-intere ranger 182 which consists of an outer casing 183 with longitudinal passages 184 for the conveyance of the compressed air, and a chamber 185 surroimding said passages for the conveyance of the cooling medium, which in this case also is the air required for forming the explosive mixture for the internal-combustion engine 200. The air which is admitted through connections 209 flows around passages 184 andv enters cylinder 200 through connection 210. 208 is a draw-oil' cock leading from trap 207. The compressed air from interchanger 182 flows through connection 211 into trap 212; thence through the inner conduit 122 of temperature-interchanger 118 and through connection 213 and inner conduitv 130 of temperature-interchanger 120. From conduit 130 the compressed air flows through valve 135 into and through conduit 137 of the so-called liquefier. The lower end of conduit 137 is connected to separator 140 from which connection 141 leads te a trap 142, and connection 151 and throttle-valve 152 to a thermo-dynamic expansion device 153. A connection. 214 and valve or cock 215 lead from separator 140 to the outside of the casing which incloses the separator. The trip 142 is connected to receiver 150 by pipe 149, and the exhaust side of the engine 153 is also connected to receiver 150 by connection 216. 217 isa. valve controlling communication between separator 140 and trap 142. The receiver 150 is connected by ipe 169 tothe lower .end of conduit 160 w `ch envelops or incloses conduit 137. The upper end of said conduit connects by ipe or channel 171 to one end of` the outsi e casing or conduit 121 of temperature-interchanger `118. The other end' is connected by conduit 173, valve 1,74 and conduit '175 to the intake side of thelow vpressum cylinder 201. The. gages 168 lndicate the pressures in separator 140 and receiver 150. 125 and 126 areconnections for the circulation of a refrigerating medium through the outer casing 131 which envelops conduit 130 of section 120. 1247 and 128 are traps with outlet cocks 133 located at the loWermost points of conduits 122 and 130. The whole system requiring protection from heat is properly insulated in the Well-known manner.

The operation is as follows z-Before starting the compressor 1, the inner and outer conduits 130 and 131 of section 120 are cooled down to a temperature lower than 20 F. by the circulation of some refrigerating medium such as expanded ammonia, carbon dioxid, or cooled brine. When this is done then the compressor is started and valve 21.7 is closed. The compressed air from cylinder 202 flows through conduit 206 into trap 207 Where it deposits the oil used for lubricating the compressor cylinders and also part of the moisture. This oil and condensed moisture can be removed from trap 207 through valve or cock 208. From trap 207 the compressed air flows through the passages 184 of cooler 182 where it interchanges temperature with the air drawn in by cylinder 200 of the intern alcombustion engine, as heretofore described. The compressed air leaves the cooler 182 .at about the temperature of the atmosphere and flows through the inner conduits 122 and 130 of temperature-interchangers 118 and 120, then c through conduit 137 of the countercurrent coil of the so-called liqueer in the mannerl heretofore described. From conduit 137 the compressed air flows through separator 140, connection 151 and throttlevalve 152 into the thermodynamic engine 153, Where it is made to expand adiabatically, or nearly so, to about atmospheric pressure. In the process of expansion the air performs external Work and drops lin temperature. The cold expanded air from engine 153 is discharged into receiver 150, and it Hows through connection 169 into conduit 160 Which envelops or .surrounds conduit 137. The cold expanded air fiows through conduit 169 in a direction opposite to that of the flow of the compressed air in conduit 137, and by doing so it absorbs heat from the latter and makes thecooling effect of the compressed air accumulative to such a degree that upon expansion through motor 153 part of it liquefies. When the cold vapor of the temperature of liquid air begins to flow reduces the temperatureof the compressed air in the lo'wer part of conduit 137 to such a degree thatv part of it assumes the liquid state. The presence of liquid in receiver 140 may be detected b opening valve 215; valve 217 is then opene and the li uid from separater 140 isallowed to flow t rough connection 141-into trap 142; thence through connection 149 into receiver 150 in the manner described for tra 42 of Fig. 1. The liquid air may `be .wit drawn from receiver 150 through valve 164 and connection 165, and the unliqueed air, together with the prodthrough connection 169 into conduit 160, it

r duit 160.

uct of evaporation of the liquid in receiver 150, is made to flow in the manner heretofore described through connection 169 and con- It may be observed that since the compressed air enters into conduit 137 at a temperature lower than 2.0o F., the expandedair leaving conduit 160 must be of a ltemperature somewhat lower than that of the compressed air, and therefore this expanded cold air, which is still of a low temperature, can be used-for cooling the compressed air flowing through the inner conduit 122 of section 118. Accordingly, the expanded cold air upon leaving conduit 160 flows through connection 171 and the outer conduit 121 of section 118, and in a direction opposite to that of the compressed air, and by doing so it absorbs heat from the latter. The expanded air on leaving theouter conduit 121 of section 11S may be discharged into the atmosphere through valve 190, or it may be allowed to flow through connection 173, valve 17 4 and connection 175, to the intake end of the low-pressure cylinder 201 of the compressor.

It is to be understood that although the circulating refrigerant' is shown in Fig. 5 as cooling the compressed air in section 120, and the cold expanded air from the liquefier as cooling the compressed air flowing through section 118, the system may be reversed; the refrigerating medium may be used for cooling section 118, and the cold expanded air from the liquefier may be made to cool section 120.

In large plants it may be desirable and profitable to perform both the above described expansions adiab atically, and the expansion means, separators, traps, etc., placed outside of the liquefier proper, properly 'insulated, as shown in Fig. 7. The lower` part of conduit 370 is connected by'header 380 and pipe 390 to separator 400, the upper part of which is connected by pipe 510-and throttle-valve 520 to motor 530. 420 is a trap, and connection 410 and valve 490"L control communication between separator 400 and trap 420. 420* is a pipe and valve leading from bottom of separator 400. 490 is a connection leading from trap 420 to separator 500, and 560 is a connection leading from the exhaust side of motor 530, also to separator 500. From separator. 500, pipe 690 and valve 590 control communication to conduit 600; pipe 620 and valve 610 control communication to motor 800, and connection 570 leads to trap 580. Pipe 640 and valve 57 0*EL control communication between trap 580 and receiver 63,0, and 700 is a connection between the exhaust end of motor 800 and receiver 630.v Pipe 660 leads from receiver 630 to the outer conduit 670. 650SL is a valve, and 650 is a pipe leading from receiver 630 for the discharge of liquid. 680 are pressure gages connecting with separators 400 and 500, respectively, and receivers '630. The operation is the same as described for Fig. 1, except that the second expansion is also performed by thermodynamic means, and the liquid and gas from the thermodynamic means 800 flow into receiver 630 from which the liquid may be withdrawn through valve and connection (550l and 650, and the gas returned by connection 660 to the outer conduit 670, as before described.

What I claim is 1. In a gas liquefying system, means for compressing and coolingI gas, a liquefied gas separator a trap having a connection therewith and adapted to separate and automatt compressing and cooling gas, la liquefied gas .I

separator a trap having a connection therewith and adapted to separate and automatically remove the liquefied gas from thel cooled compressed gas, an expansion device connected to receive gas from said separator s.

and operating to partially liquefy the gas in the expansion thereof, a receiver connected to the low pressure side of the expansion dcvice adapted to separate the liquefied from the unliquefied gas and means for withdrawing the liquefied gas from said receiver.

3. In a gas liquefying system, means for compressing and cooling gas, a separator adapted to separate liquefied gas from the cooled compressed gas, a trap connected lo the separator and adapted to remove the liquefied air, an expansion device connected to receive gas from the separator and operating to partially liquefythe gas in the expansion thereof, a receiver connected to the low pressure side of the expansion device and adapted to separate the liquefied from the unliquefied gas after expansion.

4. In a gas liquefying system, means for compressing and cooling gas, a separator 3 adapted to separate liquefied gas from the cooled compressed gas, a trap connected to the separator and adapted to remove the liquefied gas, an expansion device connected to receive gas from the separator and operating to partially liquefy the gas in the expansion thereof, a receiver connected to the low pressure side of the expansion device to separate the liquefied from the unliqueficd gas, and means for withrilrawing the liquefied gas from said receiver.

5. In a gas liquefying system, means for compressing and cooling gas, a liquefied gas separator a trap having a connection therewith and adapted to separate and automat- .llC

ically remove the l'liquelied gas from the cooled compressed gas, a thermodynamic engine connected to receive gas from said separator and operating to partically liquefy the gas in the expansion thereof, a receiver connected to the low pressure side of the thermodynamic engine adapted to separate the liquefied from the unliquefied gas after eXpansion.

6. In a gas liquefying system, means for compressing and cooling gas, a liquefied gas separator a trap having a connection therewith and adapted to separate and automatically remove the liqueiied gas from the cooled compressed gas, a thermodynamic engine connected to receive gas from said separator and operating to partially liquefy the gas in the expansion vthereof in said engine, a receiver connected to the low pressure side of the engine adapted to separate the liquei'ied from the unliquefi'ed gas and means for withdrawing the liquefied gas from said receiver.

7. In a gas liquefying system, means for compressing and cooling gas, a separator adapted to separate liquefied gas from the cooled compressed gas, a trap connected to the separator and adapted to remove the liquefied gas, a ythermodynamic engine connected to receive gas from the separator and operating to partially liquefy the gas in the expansion thereof in'said' engine, a receiver connected to the low pressure side of the engine and' adapted to separate the liqueiied from the unliqueiied gas after expansion.

`8. In a Agas liquefying system, means for compressing and cooling gas, a separator adapted to separate liquefied gas fromthe cooled compressed gas, atrap connected to the separator and adapted to remove the liquefied gas, a thermodynamic engine connected to receive the gas from the separator and operating-to partially liopiefy4 the gas in the expansion thereof in said engine, a receiver connected to the low pressure side of the engine adapted to separate the liquefied from the unliq-ueed gas, and means for WithdrawineI the liqueiied gas from said receiver.

9. In a gasl liqueffying system, means for compressing and cooling gas, a separatory adapted 'to-separate liquefiedgas from the cooled compressed g-as,y a thermodynamic engine connected to .receive gas from the separator and adapted to partially'liquefy the gas in the expansion thereof insaid engine, a throttle valve located on the high pressure side of the engine, and areceiver connected to receive the exhaust from the engine and adapted vto separate the liquefied from the unliqueiied gas after expansion.

10. In a gas liquefying syste-m, means for compressing andV cooling gas, a separator adapted to separate liquefied. gas'froin the cooled compressed gas, a thermodynamic engine connected to receive gas from the separator and adapted to partially liquefy the gas in its passage through the engine, a throttle valve located on the high pressure side of the engine, a receiver connected to rec-eivethe exhaust from the engine, and means for withdrawing the liqueiied gas from said receiver.

11. In a'gas liquefying system, means for compressing and cooling gas, a liquefied gas separator, a trap having a connection therewith and adapted to separate and automatically remove the liquefied gas from the cooled compressed gas, a thermodynamic engine connected to receive gas fioin said separator and adapted to partially liquefy the gas in the expansion thereof in said engine,`a throttle valve located on the high pressure side of the engine, a receiver connected to receive the exhaust from the engine and adapted to separate the liquefied from the unliqueii ed gas after expansion` 12. .In a gas liquefying system, means for compressing and cooling gas, ailiqueiied gas separator, a trap having a connection therewith and adapted to separate and automatically remove the liqueied gas from the cooled compressed gas, a thermodynamic engine connected to receive the gas from said separat-or and adapted to partially liquefy the gas inits passage through the engine, a throttle valve located on the high pressure side of the engine, a receiver connected to receive the exhaust from the engine, and means for withdrawing the liquefied gas from said receiver.

13. In a gas liquefying system, means for compressing and cooling gas, a separator adapted to separate the .liquefied gas from the cooled compressed gas, a trap connected to the separator and adapted to remove the liquefied gas, atherniodynamic engine connected to receive gas from the separator and adapted to partially liquefy the gas in its passage through the engine, a throttle valve located'on the high pressure side of the engine, a receiver connected to the outlet of the engine, and means for withdrawing liquid from said receiver.

14. Ina gas liquefying system, means for compressing and cooling gas, counter-current temperature interchanging means, a separator connected to the high pressure channel of the .counter current means and adapted to separate the liquelied from the unhquefied gas, a thermodynamic engine connected to receive gas from the separator', a throttle valve located on the high pressure side of the engine, a receiver connected to the low pressure side of the engine, and means for directing the iow of the unliquefied gas from the receiver through the low pressure channel of the counter-current means.

15. In a gas liquefying system, means for compressing and cooling gas, counter-current tempera-ture interchanging means, a separator connected to the high pressure channel of the counter current means and ada ted to se aratetheliqueiiedfromtheunli ue edgas, atlhermodynamic engine connecte to receive gas fronrthe separator, a throttle valve located on the high pressure side of the engine, a receiver connected to the low pressure side of the engine, :and means 'for directing the flow of the unliquefied gas from the receiver through the low pressure channel of the counter-current means, and means for withdrawing the liquefied gas from said receiver.

16. In a gas liquefying system, means for compressing and cooling gas, a separator adapted to separate the liquefied gas from the cooled compressed gas, a thermodynamic engine connected to receive gas from vthe separator, a throttle valve located on the high pressure side of the engine, a receiver connected to the low pressure side of the engine, and means for withdrawing the liquefied gas from the receiver.

17. A liquefying system for gases comprising expansion cooling means, self-intensive counter current conduits connect-ed to said eX- pansion means, a separator located between the high pressure conduit of the counter current means and the expansion means, a receiver connected to the low pressure side of the expansion means for receiving the eX- haust therefrom, and a valved connection around the expansion means connecting the separator on the high ressure side of the eX- pansion means with tie receiver on the low -pressure side of the expansion means.

p 18. A liquefying system for gases, comrprising expansion cooling means, a receiver aving a connection therewith, self-intensive counter current conduits connected to said expansion means, a separator located between the high pressure conduit of the counter-current means and the expansion means, and a connection around the expansion means controlled by a valve operating automatically to open and allow passage of fluid from the separator to the receiver.

19. In a gas li uefying system, the combination of means or cooling'and compressing said gases, and a gas liquefier comprising high and low pressure counter-current conduits for partial y liquefying said gases, a liquefied gas separator receiving from said high pressure conduit the liquefied and unliqueied portions of said gases, a thermo-dynamic engine having a valved connection with said separator, a receiver connected with the low pressure side of salid engine and a conduit controlled by a hand valve and an automatic liquid trap and connecting the high pressure side of said engine with said receiver.

20. In a gas liquefying system, a liqueiied gas separator, a thermo-dynamic engine having a valved connection with the gas inlet of said separator, and a valve controlled conduit connection around said engine between the high and low pressure sides of the same.

21. In a gas liquefying system, means for compressing and cooling gas, counter-current temperature interchanging means, a separator connected to the high pressure channel ofthe counter-current means and adapted to separate the liqueed from the unliqueiied gas, an expansion device connected to receive gas from the separator, a receiver connected to the low pressure side of the expansion device and adapted to separate the liqueiied from the unliqueiied gas, means for discharging the liquefied gas from the separator connected to the high pressure side of the expansion device into the receiver connected to the low pressure side of the expansion device, means for directing the How of unliqueiied gas from the receiver through the low pressure channel of the counter-current means, and means for withdrawingthe liquid from the last named receiver.

22. Ina gas liquefying system, means for compressing and coohng gas, counter-current temperature interchanging means, a separator connected to the high pressure channel of the counter currentmeans and adapted to separate the liqueiied from the unliquefied gas, a thermodynamic engine connected to receive gas from the separator, a receiver connected to the low pressure side of the thermodynamic engine and ada ted to separate the liquefied from the unhqueiied gas, means for discharging the liquefied gas from the separator connected to the high pressure side of the thermodynamic engine mto the receiver connected to the low pressure side of the expansion device, means for directing the flow of unliqueiied gas from the receiver through the low pressure channel of the counter-current means, and means for withdrawing the liquid from the last named re- `ceiver.

23. In a gas liquefying system, means for compressing and coohng gas, counter-current temperature interchanging means, a separator connected to the high pressure channel of the counter current means and ada ted to separate 'the liquefied from the unhqueiied gas, a thermodynamic engine connected to receive gas from the separator, a valve located on the high pressure side of the engine, a receiver connected to the low pressure side ofthe thermodynamic engine and adapted to separatev the liquefied from the unliqueiied gas, means for discharging the liquefied gas rom the separator connected to the hlgh ressure side of the thermodynamic engine mto the receiver connected to the low pressure side of the thermodynamic engine, means for directing the flow of unliquefied' gas from the receiver through the low pressure channel of the counter-current means, and means for withdrawing the liquid from the last named receiver.

24. In a gas liquefying system, means for compressing and cooling gas, counter current gine, an expansion device adapted to expandf part of the gas from said separator from an intermediate to a low pressure, a receiver Y adapted to receive the partially liquefied gas from the\ expansion device,` means for connecting the intermediate pressure separator from the intermediate pressure channel of the counter current means, means for connecting the low pressure receiver with the low pressure channel of the counter current means, and means for connecting the intermediate pressure separator With the loW 'pressure receiver.

25. In a gas liquefying system, means for compressing and coolinggas, counter current temperature interchan ging means comprising high, intermediate and low pressure channels, a thermodynamic' engine propelled b the compressed gas flowing through the high pressure channel of the counter current means, adapted to expand the gas to an intermediate pressure, a separator adapted to v receive the partially liquetedgas from the engine, Aan expansion device adapted to. ex-

pand part of ,said gas from the separator from an intermediate to a low pressure, a receiver adapted to receivethe partially liquefied gas from the expansion device, means for connecting the intermediate pressure-separator with the intermediate pressure channel of the counter current, means for connecting the low pressure receiver with the low pressure channel of the counter current meana'means for connecting the intermediate pressureseparator with the loW pressure receiver, and means for withdrawing liquid from the'low pressurel receiver.I

26. In a gas liquefying system, means for compressing and cooling gas, high and low pressure counter current `enduits, said high pressure conduit receiving the compressed cooled gas at high pressure, a separator connected to the said high pressureconduit to separate liqueied gas therefrom, a thermodynamic engine connected to receive and partially liqueiy the gas from the separator, a separator connected to the outlet of the engine to separate liquid therefrom, a free expansion device connected to the last-named separator to receive and expand the gas therefrom, a receiver connected to receive the partially liquefied gas from the free expansion device, means for withdrawing liquid from said receiver and a connection from the low pressure side of the engine to the low.

27. In a gasmliquefying system, means for compressing and cooling gas, high and low pressure counter current conduits, said high pressure conduits receiving the compressed cooled gasat high pressure, a separator connected to the said high pressure conduit to separate liquefied gas'therefrom, a thermodynamic engine. connected to 'receive and partially liquefy the gas from the se arator,

a separator connected to they outlet o the engine to separate liquid therefrom, a free expansion device connected to the last-named separator to receive and expand the gas therefrom,- a receiver connected to receive the partially liquefied gas from the free exansion device, a connection between the ast-named separator and said receiver, including a trap, means for withdrawing liquid from said receiver, and a connection from the low pressure side of the engine to the loW pressure conduit of the counter current'apparatus. f

28. In a gas liquefying system, means for compressing and cooling gas, high and low pressure counter current conduits, said high pressure conduit receiving the compressed cooled gas at high pressure, a separator connected to the said high pressure conduit to separate liquefied gas therefrom, a thermodynamic engine connected to receive and' partially liquefy the gas from the separator, a separator connected to the outlet of the engine to separate liquid therefrom, a free expansion device connected to the last-named separator to receive and expand the gas therefrom, a receiver connectedto receive the partially liqueed gas from the free expansion device, a connection between the ast-named separator and said receiver, in-

cluding a trap and a manually-operated valve, means for withdrawing liquid from said receiver,1 and a connectlon from the low pressure side of the engme to the low pressure `conduit of the counter current apparatus.

29. In a gas liquefying system, means for compressing and cooling gas, high and low pressure counter .current conduits, said high pressure conduit receiving the compressed cooled gas at high pressure, a separator connected tothe said high pressure conduit to separate liquefied gas therefrom, a thermodynamic engine connected to receive and partially liquefy the gas from the separator, a separator connected vto the outlet of theengine to separate liquid from the partlally liquefied gas, a free exiansion devlce con- .nected to the last-name separator to receive and expand the gas therefrom, a receiver connected to receive the partially llquehed 'gas from the 'free expanslon device, means for withdrawing the liquid from said receiver, a connection from the low .pressure side ol" the engine to the lower pressure part of the counter current apparatus, andan envelop for the counter current conduits connected to the low pressure side of the free expansion device. i

30. The combination of means for compressing and cooling gas, high and lower pressure counter current conduits, said high pressure conduits connected to receive the cooled compressed gas at high pressure, a plurality of expansion devices connected to receive the gas successively, a separator for liquefied gas connected in advance of each of the eX- ansion devices, and a return connection rom the low pressure side of successive eX- pansion devices to parts of the counter eurrent conduits of successively lower pressure, and means for withdrawing gas from each of such parts. f

' 31. The combination of means for com.- pressing and cooling gas, counter current conduits connected to receive the cooled compressed gas on the highpressure side, a plurality of expansion devices connected to receive the gas successively, a separator for liquefied gas connected in advanceoi each of the expansion devices, a connection between the high and low pressure sides of each expansion device including a trap and means for withdrawing liquid from said trap.

32. The combination of means forI compressing and cooling gas, counter current conduits connected to receive the cooled compressed gas on the high pressure side, a plurality of-expansion devices connected to receive the gas successively, a separator for liquefied gas connected in advance of each of the expansion devices, and a return connection from the low pressure side of successive expansion devices to parts of the counter current conduits of successively lower pressure, means for withdrawing gas from the intermediate and low pressure counter current conduits.

83. The combination of means for compressing and cooling gas, counter current conduits connected to receive the cooled compressed gas on the high pressure side, a plurality of expansion devices connected to receive the gas successively, a separator for liquefied gas connected in advance of each of the expansion devices, and a return connection from the low pressure side of successive eXpansion devices to parts of the counter current conduits of successively lower pressure, means 'for withdrawing gas from the intermediate and low pressure counter current conduits, a receiver connected to the low pressure side of the last expansion device and means for withdrawing liquid from said receiver.

34. In a gas liquei'ying system, means for compressing and cooling gas, counter-cur rent temperature interchanging means comprising high, intermediate and low pressure channels, a thermodynamic engine propelled by the compressed gas iiowing through the high pressure channel of the counter current means adapted to expand the gas to an intermediate pressure, a separator adapted to receilve the partially liqueiied gas from the engine, an expansion device adapted to expand part of the gas from said separator from an intermediate to a low pressure, a receiver adapted to receive the partially liquefied gas from the expansion'device, vmeans for conneeting the intermediate pressure separator with the intermediate pressure channel of the counter current means, and means for connecting the low pressure receiver with the. low pressure channel of the counter current means.-

In testimony whereof, I have hereunto set my hand at Los Angeles California this seventh day of December 1904.

GABRIEL A. BOBRlC-l.

In presence of FREDERICK S. LYON, ARTHUR P. KNIGHT. 

